The reason for those low sales might be due to the release event that is attached to it.
Originally the CD contains a code for the Lottery to an event where Berryz appear together with T-Pistonz+KMC.
The event however aims at children, at least the first round if I understand it correctly. Because it's more like an event for the Anime.
For whatever reason they also don't even have a handshake part like it's normal for release events.
So probably that reduced the number people bought copies to win a ticket at the lottery = low sales.
They seem to have realized that now and announced an additional handshake event.
From 7/22 (tomorrow) 11:00am on they will sell the regular edition with handshake event tickets somewhere (don't get the place).
The event will take place on the same day 7/22 and 7/23 after a performance of Berryz at Fuji-TV.
Since those CDs are extra press (not first press anymore) they will of course not contain a code for the event with T-Pistonz etc.
http://www.helloproject.com/event/1007211710_event_berryz.html